Anaplastic astrocytoma with piloid features, a novel molecular class of IDH wildtype glioma with recurrent MAPK pathway, CDKN2A/B and ATRX alterations.

Tumors with histological features of pilocytic astrocytoma (PA), but with increased mitotic activity and additional high-grade features (particularly microvascular proliferation and palisading necrosis) have often been designated anaplastic pilocytic astrocytomas. The status of these tumors as a separate entity has not yet been conclusively demonstrated and molecular features have only been partially characterized. We performed DNA methylation profiling of 102 histologically defined anaplastic pilocytic astrocytomas. T-distributed stochastic neighbor-embedding (t-SNE) and hierarchical clustering analysis of these 102 cases against 158 reference cases from 12 glioma reference classes revealed that a subset of 83 of these tumors share a common DNA methylation profile that is distinct from the reference classes. These 83 tumors were thus denominated DNA methylation class anaplastic astrocytoma with piloid features (MC AAP). The 19 remaining tumors were distributed amongst the reference classes, with additional testing confirming the molecular diagnosis in most cases. Median age of patients with MC AAP was 41.5 years. The most frequent localization was the posterior fossa (74%). Deletions of CDKN2A/B (66/83, 80%), MAPK pathway gene alterations (49/65, 75%, most frequently affecting NF1, followed by BRAF and FGFR1) and mutations of ATRX or loss of ATRX expression (33/74, 45%) were the most common molecular alterations. All tumors were IDH1/2 wildtype. The MGMT promoter was methylated in 38/83 tumors (45%). Outcome analysis confirmed an unfavorable clinical course in comparison to PA, but better than IDH wildtype glioblastoma. In conclusion, we show that a subset of histologically defined anaplastic pilocytic astrocytomas forms a separate DNA methylation cluster, harbors recurrent alterations in MAPK pathway genes in combination with alterations of CDKN2A/B and ATRX, affects patients who are on average older than those diagnosed with PA and has an intermediate clinical outcome.

Ex Vivo Intra-arterial Methylene Blue Injection in Rectal Cancer Specimens Increases the Lymph-Node Harvest, Especially After Preoperative Radiation.

BACKGROUND: The examination of as large a number of lymph nodes as possible in rectal carcinoma resectates is important for exact staging. However, after neoadjuvant radiochemotherapy (RCT), it can be difficult to obtain a sufficient number of lymph nodes. We therefore investigated whether staining with methylene blue via the inferior mesenteric artery can lead to an increase in the yield of lymph nodes in rectal carcinoma tissue after neoadjuvant RCT. METHODS: In a prospective, unicentric study rectal carcinoma resectates from three consecutive groups of patients were examined (Group I, no staining; Group II, staining with methylene blue; Group III, again no staining). The numbers of lymph nodes examined were compared (a) between the groups and (b) between patients who had not, or who had, received neoadjuvant RCT. RESULTS: In all, 75 rectal carcinoma preparations were assessed. The yield of lymph nodes investigated before the use of staining (Group I) increased when staining was introduced (Group II), both for the patients without neoadjuvant RCT (20.9 vs. 31.3, p = 0.018) and for those who did receive this (15.0 vs. 35.1; p = 0.003). After withdrawal of the staining procedure (Group III), the lymph-node yield remained high for the patients without neoadjuvant RCT (31.3 vs. 30.4; p = 0.882), but it reverted to a lower value for those who did receive neoadjuvant RCT (35.1 vs. 24.2; p = 0.029). Before the introduction of staining (Group I), significantly fewer lymph nodes were examined for patients who received neoadjuvant RCT (15.0 vs. 20.9; p = 0.039). However, with staining (Group II), no difference was found associated with the use or non-use of neoadjuvant RCT (31.3 vs. 35.1; p = 0.520). CONCLUSION: The use of methylene blue staining of rectal carcinoma preparations leads to a significant increase in the number of lymph nodes examined after neoadjuvant RCT. This can be expected to improve the accuracy of lymph-node staging of neoadjuvant-treated rectal carcinoma.